A distributed antenna system (“DAS”) may be used to extend wireless coverage into structures where RF penetration directly from the base station is limited. A DAS can communicate signals between a base station and remote antenna units positioned in the structure being serviced by the DAS. The DAS may communicate signals from multiple technologies in the same band. For example, the DAS may communicate signals in the same frequency band used by both a Global System for Mobile Communications (“GSM”) standard and a wideband CDMA (“WCDMA”) standard.
A mobile device may be positioned in the area serviced by the DAS. The mobile device may be serviced by an external base station for an operator that does not communicate via the DAS. The external base station may communicate with the mobile device may communicate via a telecommunication technology utilizing the same frequencies in an uplink frequency band as utilized by the DAS. The mobile device may be close to a remote antenna unit of the DAS and distant from the external base station. The mobile device may transmit uplink signals to the external base station at high power levels to overcome path loss caused by the distance between the remote antenna unit and the external base station. The mobile device transmitting uplink signals to the external base station at high power levels can overdrive a receiver of the remote antenna unit. A narrowband GSM signal may overdrive a receiver of a remote antenna unit. Overdriving the receiver of a remote antenna unit can cause inter-modulation distortion, thereby degrading channels adjacent to a narrowband GSM channel.
Prior solutions for handling narrowband interfering signals have involved reducing the gain of the receiver in overdriven remote antenna units until the intermodulation or other distortion is reduced to an acceptable level. Such solutions can present disadvantages, such as increasing the noise figure of the receiver. Increasing the noise figure of the receiver for one or more remote antenna units can desensitize the receiver for other mobile devices being serviced by the DAS.